The present method and apparatus are based upon sheet slitting and grooving geometries disclosed in depth in the above set forth related applications, which are each incorporated herein by reference in their entireties. In these related applications several techniques or manufacturing processes for forming slits and/or grooves that will precisely control bending of sheet material are disclosed. The emphasis in these related applications is in connection with the use of slits which penetrate completely through the sheet of material. Both slits and grooves or displacements can be provided which control bending by reason of their configuration and the orientation of the bending straps at the ends of the slits or grooves. For slit sheets, edge-to-face engagement of the sheet of material on opposite sides of the slits also is employed to achieve precision in the location of the bends.
These prior related applications also contemplate the use of grooving of the sheet material by various techniques in order to have a sheet of material in which there is a continuous web or membrane at the bottoms of the grooves. Such a web or membrane will allow the bent sheet material to be fluid-tight across the bend line for applications which require containment of a fluid and for use in electronic equipment housings as electromagnetic interference (EMI) shielding.
While in the prior related applications the emphasis was on controlling the location of the bend precisely by using edge-to-face interengagement of the sheet material on opposite sides of the slits or grooves, it has been discovered, and it is an important feature of the invention of the present application, that controlling of the positioning of the bend line on the sheet of material can be accomplished by a combination of groove location and bending straps configuration. Thus, a balancing of bending forces can be set up that will control location of the bend line without the need for edge-to-face interengagement of the sheet material on opposite sides of a slit. This grooving technique allows fluid-tight and EMI shielding housings to be constructed by bending sheet material with grooves and bending straps that control bending with sufficient precision that complex housings for electronic products and fluid-containing applications can be achieved.
Grooving of sheet material in order to facilitate bending is broadly known in the patent literature. Thus, continuous grooves which do not penetrate through a sheet have been used to cause bending of the sheet along the approximate centerline of the grooves. Similarly, discontinuous grooves which are aligned along the bend line also have been used. Finally, grooves which are laterally and longitudinally-offset along opposite sides of a bend line also have been employed as strategy for bending sheet material. Typical of the patent references disclosing these types of grooving techniques is U.S. Pat. No. 6,640,605 to Gitlin et al.
In the Gitlin et al. patent, however, the bending webs between discontinuous grooves have centerlines which are parallel to the desired bend line. This approach requires that the bending straps between grooves undergo substantial twisting, while the continuous webs at the bottom of the grooves are being bent. The approach results in a bend line which has less precision in its location than would be otherwise desirable.
Accordingly, it is an object of the present invention to provide a method of preparing sheet material for bending or folding along a bend line which is capable of producing structures that are fluid-tight, can act as EMI shielding structures, have improved appearance, have additional strength and are corrosion resistant.
Another object of the present invention is to provide a method of preparing sheet material for bending or folding, and the resultant sheet, and the bent or folded structure, which have improved versatility in the ability to vary the bending characteristics and the materials which may be bent into structures.
A further object of the present invention is to provide a method for bending or folding a sheet material, the sheet therefor, and the resultant bent or folded structure formed using the sheet, which employ groove and bending strap configurations in order to control bend line location by balancing the forces in the bending straps during bending.
The grooved sheet material and method for preparing a sheet for bending or folding of the present invention have other objects and features of advantage which will be set forth in more detail in, and will be apparent from, the following Best Mode of Carrying Out the Invention, as exemplified and illustrated by the accompanying drawing.